Gas lift valve damper



Nov- 24, 1 59 H. E. MQGOWEN, JR

GAS LIFT VALVE DAMPER Filed Jan. 20, 1955 INVENTOR. Q, 01%

' ATTORNEY f/aro/a MCGOWE/ L/ ;.f in? a Y Application January 20,1955, SerialNo. 483,151

2,914,078 I GAS LIFT VALVE DAMPER Cameo, Incorporated, Houston, Tex., a corporation of p 2 Claims. (Cl. 137-155) Well fluids are often produced by introducing or imposing on the liquid "a lifting gas under pressure. A typical installation involves the use ofa surface located controller of pressure gas supplied to the annular space surrounding the tubing string, and the wall of the string at s'pac.:d elevations has flow openings normally closed by pressure responsivcvalves set to open at predetermined gas lift pressures, each differing from one another, for the passage of pressure lift gas sequentially at successive elevations into the oil column within the tubing string. Pressure responsive control valves in general use 'areconstructed with opposing faces, one exposed to lifting gas pressure and sometimes to liquid pressure as well-and the'other face sealed off from pressure lifting gas action by afiexible metal bellows between the valve andthe vave housing, with either or both a coiled spring and a' confined gas under pressure arranged to act on the valve with a givenforce in elasticopposition to gas lift pressure. Occasionally, and especially when the opposing forces are near thecritical point of balance and due to sudden surge or otherwise, the floating valve has a tendency to violent flutter, which places strain on the ing which accurately maintains valve travel in line with the valve seat and is constituted by a downwardly pro .jecting stem fixed to the housing inside the sealed chamber defined by the bellows for limited slidable reception within a valve carried pocketso that the pocket and stem, in addition to serving as a guide and a stop for valve movement, alford a dashpot check for the rate of valve movement to minimize the inception of and to damp valve chatter.

A further object of the invention is to provide a gas lift valve in which the guide stem and pocket are so arranged that valve movement varies the effective volume of the pocket and the close fit of the bearing surfaces restricts fiuid Bow to and from the space within the pocket to thereby retard valve movement and rapid change in direction of valve movement. By design, the guide stem receiving pocket in the top of the movable valve is a part of the beflows confined chamber and is located at the bottom thereof. The chamber may contain a small quantity of liquid, such as a thin oil, in an amount approximating or slightly in excess of the maximum capacity of the pocket. Following a liquid expulsion from the pocket upon valve opening movement, which decreases pocket volume, the liquid will collect by gra ity immediately above the top of the pocket and whenever pocket volume increases upon valve travel toward its seat, the liquid wil be drawn back into the pocket by suction beneath the guide stem. While the creation of suction on the valve closing structure serves as a retardant opposing rapid closing movement, its retarding force obviously is greatly exceeded by the retardation force opposing equally rapid opening move- ,un Mam -9 2,914,078 Patented Nov. 24,

'ment ofthe valve bypositive displacement of pocke entrapped-oil through the restricted passage around the guide stem. Oil flow through the restricted path between the bearing surfaces maintains these surfaces constantly lubricated for a prolonged wear life, and the How restriction retards the rate of valve travel in both directions and damps sudden changes in direction of travel. Gravity and suction return of collected liquid will be assisted when the bellows enclosed chamber contains a pressure gas whose primary function, alone or in combination with a spring, is to offer elastic resistance to the pressure action on the valve of the lifting gas, whose flow is controlled by the valve in the well fluid lifting operation.

The invention will be better understood upon reference to the accompanying drawing, wherein Figure 1 is a vertic'al sectional view showing fragments of a conventional well installation, and Fig. 2 is a vertical sectional view of theim roved valve structure as viewed on line 22 of Fig. 1.

In the usual oil well installation, a series of valves are carried in spaced apart relation, either on the inside or the outside of the tubing string, dependent on whether the liftgas is to be supplied to the inside or the outside of the tubing wall for lifting oil on the opposite side of the wall. Thevalve assemblies may be attached to tube sections at the time of string installation, or they may be of the retrievable type for insertion or removal by a wire suspended line and chuck connection into a specially designed mandrel section so that valve installation and replacement can be made without the necessity for pullin the string from an operating well. A retrievable installation is shown in Fig. 1, wherein the tubing string mandrel1 is received within the well casing 2 and has a lateral offset containing a valve mounting sleeve 3. @T he opening through the mandrel wall includes an entry 1 port 4 and an outlet port 5 for the flow of gas, as indicated by the arrows, under control of the valve assembly pocketed. within the sleeve 3. For connection with a suitable tool on the end of a wire line, the valve assembly .axialpassage 10 for communication with the mandrel outlet: 5 and provides at its upper end a seat fora valve tip 11, movable in a valve chest defined by the section 8 having a lateral opening 12 for communication with the entry passage 4. In addition to the valve tip 11, the movable valve includes a plunger 13 exposed to the lift gas pressure on its under side and sealed off from the pressure on its upper face by means of an annular, thin metal bellows wall 14 secured and sealed at one end to the upper face of the head 13 and secured at its upper end to the lower end of the housing section 7.

In the simplified embodiment of the invention here illustrated, downward valve seating action is controlled solely by gas under pressure contained within the variable volume chamber defined by an enlarged space 15 within the tubular section 7 of the valve body or housing and closed at the bottom by the movable valve and bellows seal 14. At its upper end the enclosed chamber 15 is plugged and sealed by the customary one-way valve, which allows the chamber to be charged to a given pressure with an inert gas, such as nitrogen, and whose elastic force urges the valve toward its seat.

Within the bellows enclosed chamber and centrally of the upper face of the valve plunger 13 is an upwardly opening pocket 16 which slidably receives a stem projection 17 which extends centrally of the bellows and is rigidly secured at its upper end by screw threads or the like within the tubular section 7 so as to depend downwardly therefrom. The stem 17 has a close sliding fit with the side wall of the pocket 16 as a guide bearing and with a clearance of approximately five-thousandths of an inch. The bottom wall of the pocket 16 and'the lower end of the stem 17 provide abutment stop surfaces to limit upward movement of the valve and axial collapse of the bellows 14. An opening 18 is drilled centrally of the stem 17 and has one or more lateral ports 19 leading from the bottom thereof for communication between the interior of the bellows 14 and the enlarged chamber in the housing section 7. Vertical travel of the valve plunger 13 with respect to the stem 17 varies the volume of the pocket 16, and the restriction between the bearing surfaces allows fluid flow to and from the pocket during relative valve travel so that there is provided a dashpot or valve motion check against flutter tendency.

Advantage can be taken of the position of the dashpot 16 at the bottom of the gas compression chamber for both supplying constant lubrication of the guide bearing surfaces and an effective motion check action by introducing into the chamber, in addition to compressed gas, a liquid and preferably a light oil. Specific gravity will keep the oil separated from the inert gas and at the bottom of the chamber for flow into the pocket 16. Upward travel of the valve will then be resisted not only by the elasticity of the compressed gas within the chamber but also by the liquid body trapped within the pocket 16, which must be displaced upwardly through the small bearing clearance space. On the valve return stroke, the oil previously expelled and which will have collected by gravity around the upper end of the pocket will be drawn by suction within the pocket and pushed by the compressed gas back into the pocket. Valve movement in either direction is at a slow rate, such that vibration is unlikely to be set up and thus flutter is minimized without. disturbing the fluid control operation of the valve.

From the above description it will be seen that there is provided a gas lift valve assembly wherein a valve pocket formed as a part of the bellows sealed chamber receives a projected piston stern for a combined guide for valve movement in relation to the valve seat and a fluid dampener for valve movement to and from its seat. A preferred embodiment has been shown and discussed without intention of limiting the scope of the invention as set out in the appended claims.

What is claimed is:

1. A flow valve assembly for pressure gas injection into a well production conduit, including a pair of juxtaposed inner and outer concentric tubular walls, the inner of which is a flexible bellows having its upper end fixed to the outer wall and partitioning the space within the outer tubular wall into an upper variable volume sealed chamber and a lower valve chamber for controlled gas flow therethrough, a valve support carried by the movable free end of the bellows and formed interiorly of the sealed chamber with an upwardly opening and otherwise closed guide pocket, a dependent stem fixedly mounted by said outer wall and projected downwardly through said bellows into close fitting reception within said guide pocket to resist lateral deflection of said bellows free end into wiping contact with said outer wall and to present a bottom terminal face engageable by the guide pocket bottom as a stop abutment to limit the bellows free end upward travel, a relatively small volume of liquid filling the guide pocket space unoccupied by said fixed stem and a lower fraction of the bellows interior to a level which throughout the range of said travel is considerably below the upper fixed end of the bellows, and a relatively large volume of gas occupying the remainder of the bellows interior as elastic resistance to upward travel of said bellows free end.

2. A flow of control unit for pressure gas injection into a well production conduit, including a normally downwardly biased valve member having an area on its underside exposed to upward force of pressure fluid to be controlled, a mounting body therefor, a flexible bellows seal having oneend anchored on the mounting body and its opposite free end connected with the valve member for sealing its upper side from action thereon of said pressure fluid, a stem fixed on the mounting body and projected axially downwardly through the bellows and closely fitted to a dead-ended pocket in the bellows sealed upper side of said valve member for guiding the free end of the flexible bellows against lateral deflection and for steadying axial response of said bellowsfree end to opposing forces on the valve member and a body of liquid confined within and of a volume considerably less than the volume of said bellows for passage toand from said guide pocket and solely through the clearance between the closely fitted stem and dead-ended guide pocket.

References Cited in the file of this patent UNITED STATES PATENTS 

